Which two solutions have the same concentration?

(a) 55.45 g NaCl/L solution; 

(b) 5.545 g NaCl/100 g solution; 

(c) 55.45 g NaCl/kg water;

(d) 55.45 mg NaCl/1.00 mL solution; 

(e) 5.00 mmol NaCl/5.00 mL solution.